Why Ingress manages external access in Kubernetes - Visual Breakdown

Process Flow - Why Ingress manages external access

User sends request to cluster IP

↓

Ingress Controller receives request

↓

Ingress rules check request path & host

↓

Route to Service A

↓

Service A Pod

↓

Response sent back

Ingress acts as a gatekeeper that receives external requests and routes them inside the cluster based on rules.

Execution Sample

Kubernetes

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: example-ingress
spec:
  rules:
  - host: example.com
    http:
      paths:
      - path: /app1
        pathType: Prefix
        backend:
          service:
            name: app1-service
            port:
              number: 80

This Ingress resource routes requests with host 'example.com' and path starting with '/app1' to the 'app1-service'.

Process Table

Step	Request Host	Request Path	Ingress Rule Match	Service Routed To	Action
1	example.com	/app1/home	Host matches example.com, Path prefix /app1	app1-service	Route request to app1-service
2	example.com	/app2/home	Host matches example.com, Path prefix /app1 (No)	No match	Return 404 or default backend
3	other.com	/app1/home	Host does not match example.com	No match	Return 404 or default backend

💡 Requests stop routing when no matching Ingress rule is found or after routing to the correct service.

Status Tracker

Variable	Start	After Step 1	After Step 2	After Step 3
Request Host	none	example.com	example.com	other.com
Request Path	none	/app1/home	/app2/home	/app1/home
Matched Service	none	app1-service	none	none

Key Moments - 2 Insights

Why does a request with host 'other.com' not get routed to any service?

Because the Ingress rule only matches requests with host 'example.com' as shown in execution_table row 3, so no routing occurs.

What happens if the request path does not start with the specified prefix in the Ingress rule?

The request does not match the path rule and is not routed to the service, as seen in execution_table row 2 where '/app2/home' does not match '/app1' prefix.

Visual Quiz - 3 Questions

Look at the execution table, which service does the request with path '/app1/home' and host 'example.com' route to?

A app1-service

B app2-service

C No service, returns 404

D Default backend

💡 Hint

Check row 1 in the execution_table where host and path match the Ingress rule.

At which step does the request fail to match any Ingress rule due to host mismatch?

A Step 1

B Step 2

C Step 3

D None

💡 Hint

Look at the 'Request Host' column in execution_table row 3.

If the path prefix in the Ingress rule changed to '/app2', what would happen to the request at step 1?

A It would route to app1-service

B It would not match and return 404

C It would route to app2-service

D It would route to default backend

💡 Hint

Compare the path '/app1/home' with the new prefix '/app2' in execution_table logic.

Concept Snapshot

Ingress manages external access by acting as a traffic router.
It listens for requests from outside the cluster.
Routes requests based on host and path rules.
Sends traffic to the correct internal service.
If no rule matches, returns 404 or default backend.
Ingress simplifies exposing multiple services securely.

Full Transcript

Ingress in Kubernetes manages external access by receiving requests from outside the cluster and routing them to internal services based on rules. The Ingress controller checks the host and path of each request against defined rules. If a request matches a rule, it is forwarded to the specified service. If no rules match, the request is rejected or sent to a default backend. This allows multiple services to be exposed through a single external IP with clear routing rules.

Practice

1. What is the primary role of an Ingress in Kubernetes?

easy

A. To manage external access to services inside the cluster

B. To store configuration data for pods

C. To schedule pods on nodes

D. To monitor resource usage of containers

Solution

1. Step 1: Understand Ingress purpose

   Ingress is designed to control how external users access services running inside Kubernetes.

2. Step 2: Compare with other components

   Other components like ConfigMaps store data, schedulers place pods, and metrics monitor usage, but Ingress manages external access.

3. Final Answer:

   To manage external access to services inside the cluster -> Option A

4. Quick Check:

   Ingress controls external access = C [OK]

Hint: Ingress controls outside traffic to services [OK]

Common Mistakes:

• Confusing Ingress with ConfigMap or Scheduler
• Thinking Ingress manages internal pod scheduling
• Assuming Ingress monitors resource usage

2. Which of the following is the correct basic syntax to define an Ingress resource in YAML?

easy

A. apiVersion: v1\nkind: Service\nmetadata:\n name: example-ingress\nspec:\n selector:\n app: example\n ports:\n - protocol: TCP\n port: 80\n targetPort: 9376

B. apiVersion: networking.k8s.io/v1\nkind: Ingress\nmetadata:\n name: example-ingress\nspec:\n rules:\n - host: example.com\n http:\n paths:\n - path: /\n pathType: Prefix\n backend:\n service:\n name: example-service\n port:\n number: 80

C. apiVersion: apps/v1\nkind: Deployment\nmetadata:\n name: example-ingress\nspec:\n replicas: 3\n selector:\n matchLabels:\n app: example

D. apiVersion: networking.k8s.io/v1\nkind: Ingress\nmetadata:\n name: example-ingress\nspec:\n rules:\n - host: example.com\n tcp:\n ports:\n - port: 80\n backend:\n serviceName: example-service\n servicePort: 80

Solution

1. Step 1: Identify correct Ingress syntax

   Ingress uses apiVersion networking.k8s.io/v1, kind Ingress, and defines rules with host and http paths.

2. Step 2: Check options for correct fields

   apiVersion: networking.k8s.io/v1\nkind: Ingress\nmetadata:\n name: example-ingress\nspec:\n rules:\n - host: example.com\n http:\n paths:\n - path: /\n pathType: Prefix\n backend:\n service:\n name: example-service\n port:\n number: 80 matches the correct structure with service name and port under backend. apiVersion: v1\nkind: Service\nmetadata:\n name: example-ingress\nspec:\n selector:\n app: example\n ports:\n - protocol: TCP\n port: 80\n targetPort: 9376 is a Service definition. The other options define a Deployment or incorrectly use a tcp field.

3. Final Answer:

   apiVersion: networking.k8s.io/v1 kind: Ingress spec: rules: - host: example.com http: paths: - path: / pathType: Prefix backend: service: name: example-service port: number: 80 -> Option B

4. Quick Check:

   Ingress YAML syntax = A [OK]

Hint: Ingress YAML uses rules with host and http paths [OK]

Common Mistakes:

• Confusing Service or Deployment YAML with Ingress
• Using tcp instead of http in rules
• Incorrect apiVersion or kind for Ingress

3. Given this Ingress rule snippet, what hostname will route traffic to my-service?

spec:
  rules:
  - host: app.example.com
    http:
      paths:
      - path: /app
        pathType: Prefix
        backend:
          service:
            name: my-service
            port:
              number: 8080

medium

A. app.example.com

B. example.com

C. my-service

D. app

Solution

1. Step 1: Identify the host in the Ingress rule

   The host field is set to app.example.com, which defines the hostname for routing.

2. Step 2: Understand routing based on host

   Traffic to app.example.com with path prefix /app routes to my-service on port 8080.

3. Final Answer:

   app.example.com -> Option A

4. Quick Check:

   Host in rule = app.example.com [OK]

Hint: Look for host field in Ingress rules [OK]

Common Mistakes:

• Confusing service name with hostname
• Ignoring the host field and picking path or service name
• Choosing partial strings like 'app' instead of full hostname

4. You created an Ingress resource but external traffic is not reaching your service. Which of these is a likely cause?

medium

A. The pod image is missing a label

B. The cluster has no nodes

C. The service port is set to 0

D. The Ingress controller is not installed or running

Solution

1. Step 1: Check Ingress controller presence

   Ingress resources need an Ingress controller to process rules and route traffic. Without it, Ingress does nothing.

2. Step 2: Evaluate other options

   Pod labels or service ports affect internal routing but won't stop Ingress from receiving traffic. No nodes means cluster is down, but question focuses on Ingress.

3. Final Answer:

   The Ingress controller is not installed or running -> Option D

4. Quick Check:

   Ingress needs controller to route traffic = B [OK]

Hint: Ingress needs a controller running to work [OK]

Common Mistakes:

• Ignoring the need for an Ingress controller
• Blaming pod labels for external access issues
• Confusing service port 0 with Ingress failure

5. You want to expose two services, service-a and service-b, on the same domain but different paths using Ingress. Which configuration correctly achieves this?

hard

A. Use a LoadBalancer service type for each service instead of Ingress

B. Create two Ingress resources with the same host example.com, each with one path for service-a and service-b

C. Define one Ingress with rules for host example.com and paths /a routing to service-a, /b routing to service-b

D. Expose service-a and service-b on different ports without Ingress

Solution

1. Step 1: Understand Ingress path routing

   Ingress can route different URL paths on the same host to different services using rules with multiple paths.

2. Step 2: Compare options for best practice

   Define one Ingress with rules for host example.com and paths /a routing to service-a, /b routing to service-b uses one Ingress with multiple paths, which is efficient and standard. Create two Ingress resources with the same host example.com, each with one path for service-a and service-b may cause conflicts. Options C and D avoid Ingress and don't meet the requirement.

3. Final Answer:

   Define one Ingress with rules for host example.com and paths /a and /b routing to respective services -> Option C

4. Quick Check:

   One Ingress, multiple paths = A [OK]

Hint: Use one Ingress with multiple paths for same host [OK]

Common Mistakes:

• Creating multiple Ingresses with same host causing conflicts
• Using LoadBalancer instead of Ingress for path routing
• Exposing services on different ports without hostname routing